I've seen people walking around w the prison uniform and I've been told that it was keepsaked. However, I can't seem to keepsake them myself at the rock. I can't go to a nearby bank cause I lose all the items and its pointless
help me
From what I can tell, it doesn't seem you can keepsake it any more
Players used to be able to take keepsake keys (the item, before they were added to the wardrobe interface) to the island and keepsake it, without the need to be in a safe area such as a bank
I have the outfit keepsaked, and as The Ogre stated, you should be able to drag and drop it into your keepsake box while in the prison, provided you have keys.